1. Field of the Invention
The present invention relates to a refrigerant transporting hose and particularly to such hoses suitable for use as piping for car coolers, air conditioners and the like which are employed in automotive vehicles.
2. Discussion of the Prior Art
Referring to FIG. 9, there is shown a known hose for transporting or conducting refrigerant gas such as Freon (fluorohydrocarbon). The hose has a three-laminated or layered structure consisting of an inner and an outer rubber tube 201 and 203 and a reinforcing fiber layer 202 interposed between the inner and outer tubes 201, 203. The inner rubber tube 201 is formed of acrylonitrile-butadiene rubber (NBR), chlorosulfonated polyethylene (CSM) or the like, the reinforcing fiber layer 202 is formed of polyester fiber or the like, and the outer rubber tube 203 is formed of ethylene propylene diene rubber (EPDM), chloroprene rubber (CR) or the like. Reference numerals 215 designate spiking holes which are formed through the outer rubber tube 203 so as to communicate the reinforcing fiber layer 202 with outside space. The spiking holes 215 serve to relieve the refrigerant (Freon) which has permeated the inner rubber tube 201, into the outside space, thereby preventing the hose from being swollen due to the refrigerant otherwise trapped between the intermediate fiber layer 202 and the inner and/or outer rubber tubes 201, 203. Thus, the hose is free from the problem of separation or peeling at the interfaces between the three laminates (one layer 202 and two tubes 201, 203) due to the trapped refrigerant. Being formed of rubber material except for the reinforcing fiber layer 202, the hose has a high flexibility. Accordingly, the hose can be handled with ease, for example to provide rubber piping. Moreover, the rubber hose can be connected with high gas tightness to a nipple or other joints. Rubber material, however, has a comparatively high gas permeability, that is, a comparatively low resistance to gas permeation therethrough. Therefore, the rubber hose suffers from the problem of leakage of the refrigerant gas conveyed therethrough, especially where Freon, whose molecular weight is comparatively low, is used as the refrigerant.
Referring to FIG. 10, there is shown another known refrigerant transporting hose including an innermost resin layer 304 formed of polyamide resin, such as nylon 6, which has a high resistance to gas permeation. The innermost polyamide resin layer 304, and a rubber layer 305 formed of a rubber material such as NBR and located radially outwardly of the polyamide resin layer 304, correspond to the inner rubber tube 201 of the hose of FIG. 9. The hose further includes a reinforcing fiber layer 302 formed on the outer surface of the rubber layer 305 and an outer rubber tube 303 formed on the outer surface of the fiber layer 302. Reference numerals 315 designate spiking holes similar to those 215 of the hose of FIG. 9. Having the polyamide resin layer 304 having a high resistance to gas permeation, the hose does not permit leakage of the refrigerant gas even if the molecular weight of the gas is comparatively low. However, since polyamide resin is a very rigid material, the overall flexibility of the hose is deteriorated due to the use of the rigid polyamide resin layer 304. On the other hand, if the thickness of the polyamide resin layer 304 is reduced to increase the flexibility of the hose, then the resistance to gas permeation of the hose is deteriorated.
As is apparent from the foregoing, none of the conventional refrigerant transporting hoses are satisfactory in quality.